It is known in the industry to disperse a polyamide polymer into a polyester polymer matrix. It is also known that sulfonated polyester polymers will increase the dispersion. It is also known that color bodies may form during the dispersion process and that the use of the lithium salt of the sulfonated polyester polymer reduces the color formation.
These dispersions are used in the packaging industry to create high barrier bottles. What has been observed is that when the bottles are ground up and the dispersion is exposed to a second thermal history, such as drying and re-extrusion, there can be an increase in yellow color.
While some advocate the use of phosphates, one would not typically use the phosphites, or oxidizable phosphorus compounds. It is well known that the use of oxidizable phosphorus compounds reduces the catalyst such as antimony to its elemental metal form in the polyester causing an undesirable dark color.
There exists therefore a need for a stabilizer that does not reduce the metal catalyst in the polyester polymer and that has a minimal or reduced increase in yellow color upon the second thermal history; such as would occur during the recycling operation.